ENERGY SAVINGS WITH RECIRCULATED AIR
We can estimate the energy savings that could be expected in a hospital located in the northeast. As the area of the country changes from east to west and north to south the costs used for electricity and air conditioning will also change. As an average the A/C costs go up as the heating costs go down. Therefore, this estimate should certainly be checked, however, it should end up very close to the costs in most areas; this will be true because the Northeast uses oil, which is expensive for heating and the electricity is $0.12 per kwh, used for cooling. The length of the heating or cooling seasons will also change.
PARAMETERS
Air flow =
500 cfm
Electricity
cost = $0.12
Oil cost =
$1.50/gallon
Btuh per gallon =
139,000
Heating efficiency =
84%
Equipment usage
= 12 hours per day
Usage per year =
365 days per year
Average winter
= 35 degrees F to 70 = 35 delta T
Average summer =
80 degrees F to 72 = 8 delta T
Average enthalpy =
5 btu/pound of air delta H
CALCULATION
Costs of 500 cfm exhaust =
1.085x cfm
x winter dTx1800 hrs +(1.085x cfm x summer dT + 4.5x
cfm x dH)x1800 hrs
39,000 x 0.84 x 1/$1.50 3414
btu/kwh x 1/0.12
= 1.085
x 500 x 35 x 1800 + (1.085 x 500 x 8 + 4.5 x 500
x 5 )x 1800
77,840
3414
x 1/0.12
= $439.00 + (4340 + 11250) x 1800 x 0.12/3414 = $439.00 + $986.00 = $ 1,425.00 per year
